1. Field of the Invention
The invention relates to a cryostatic microtome, or a microtome cryostat, and more particularly to a cryostatic microtome with a cryostatic chamber and a microtome arranged in the cryostatic chamber, including a specimen holder and a knife.
2. Description of Prior Art
Cryostatic microtomes of the above kind have been known for a long time. They are usually used to cut thin sections from specimens, which are then analyzed under a microscope. For this purpose, cryostatic microtomes have a cooled cryostatic chamber in which a specimen holder is located to receive a specimen to be cut, together with a knife holder that can be moved relative to the specimen holder. A knife that cuts the sections from the specimen is received in the knife holder. Cooling is required in order to cut specimens which have been prepared by freezing. The optimum temperature of the specimens to be cut is determined empirically and is different for specimens of different consistency. The cooling of conventional cryostatic microtomes with a cryostatic chamber takes place in different ways.
In a cryostatic microtome described in U.S. Pat. No. 4,548,051, which is constructed as described above, the cooling is effected by a central cooling device, which cools the air in the cryostatic chamber until the specimen to be cut has reached a suitable temperature.
WO 87/022130 likewise describes a cryostatic microtome as described above. Here the cooling takes place by means of a central cooling device in which the air temperature of the cryostatic chamber is cooled down and by an additional cooling means on the specimen holder in the form of a Peltier element by means of which the temperature of the specimen to be cut can be finely controlled.
Furthermore, cryostatic microtomes are known in the art that operate in ambient air and are not located in a cryostatic chamber. Since the knife and the specimen cannot be cooled by means of a central cooling system in ambient air, as in a closed cryostatic chamber, cooling devices located in both the specimen holder and the knife holder enable the specimen holder and the knife holder to be cooled. In such microtomes, the knife holder, and hence the knife, is cooled to a fixed, predetermined temperature, while the temperature of the specimen in the specimen holder is adjustable. Such cryostatic microtomes usually do not reach particularly low temperatures, because the warm ambient air warms the microtome too much.